The objectives of this research plan are to clarify the relationships among endocrine, paracrine and cellular events which culminate in parturition in primates. Data obtained in pregnant rhesus monkeys will provide insights into the mechanisms of normal and preterm human labor. Physiological studies of adrenocorticotropin (ACTH), corticotropin releasing hormone (CRH), androgen, glucocorticoid and interleukin (IL)-8 infusions together with blockade of androgen, estrogen and progesterone action will be carried out in chronically-catheterized, mobile, pregnant rhesus monkeys. Complementary in vitro studies of intrauterine tissues will address the following questions (1) Does premature activation of the rhesus fetal (or maternal) hypothalamic-pituitary-adrenal (HPA) axis replicate the cellular and paracrine events seen in spontaneous parturition; does it lead to preterm labor and delivery? (2) Are the effects of rising fetal plasma ACTH mediated by androgens, estrogens or glucocorticoids acting upon amnion/chorion or decidua? (3) Does intrauterine "progesterone (P) withdrawal" occur in myometrium or decidua by a gestational change in the P receptor isoforms (PR-A and PR-B) or in amnion, immune cells or uterine myocytes by nongenomic mechanisms (i.e., membrane effects)? (4) Does direct intraamniotic infusion of purified IL-8 replicate the chemotactic/paracrine manifestations of spontaneous or ACTH-induced parturition? Uterine contractility will be continuously monitored and quantified and serial samples of amniotic fluid, maternal and fetal blood will be assayed for steroid hormones, ACTH, CRH, oxytocin, prolactin, eicosanoids, cytokines, and heat shock proteins. Samples of intrauterine tissues will be obtained at delivery or cesarean section for histopathologic studies; immunohistochemistry for cytokines, sex steroid and glucocorticoid receptors and prostaglandin dehydrogenase (PGDH); quantification of mRNA (for cytokines, sex steroid receptors, 3 -hydroxysteroid dehydrogenase and cyclooxygenase isoforms) and zymography for matrix metalloproteinases. Leukocytes in amniotic fluid will be assessed by flow cytometry; their potential fetal source by amplification of Y-chromosome specific DNA. Ca2+ flux in isolated amnion, immune cells and uterine myocytes will be measured by fluorescent imaging. Computer methods will be used for on-line data acquisition and statistical analyses of waveforms, biorhythms, and hormonal trends. By comparing and integrating the physiologic, hormonal and cellular changes in experimental groups and controls, we will obtain evidence which is critical to establish the causal links responsible for term and preterm labor in a primate.